TY  - JOUR
AB  - Increased knowledege of the molecular composition of dissolved organic matter (DOM) is of great importance for an improved understanding of carbon cycling in lakes. However, such information remains limited for saline lakes. Here, DOM molecular compositions and microbial community structures were investigated in saline lakes with a full range of salinity from freshwater to hypersaline. An integrated approach, including Fourier transform-ion cyclotron resonance mass spectrometry and Illumina sequencing was employed. The results showed that in the studied saline lakes, aliphatic compounds, highly unsaturated and oxygen poor/rich compounds were the dominant DOM molecules. With increasing salinity, the molecular weight and carbon contents of the DOM molecules decreased, while their oxygen contents and carbon oxidation states increased. DOM molecular composition was significantly correlated with multiple environmental variables (i.e., chlorophyll a, salinity, pH) and with microbial components. The synergy of environmental and microbial factors exhibited great importance in explaining the variation of DOM molecular composition. Comparatively, microbial factors alone gave a much better explanation than environmental factors alone of the variation of DOM molecular composition, emphasizing the tight connection between DOM molecular composition and microbial communities. Taken together, these findings help improve our understanding of the molecular composition of DOM and its influencing factors in saline lakes.
AU  - Jiang, H.*
AU  - Lv, Q.*
AU  - Yang, J.*
AU  - Wang, B.*
AU  - Dong, H.*
AU  - Gonsior, M.*
AU  - Schmitt-Kopplin, P.
C1  - 64833
C2  - 52512
TI  - Molecular composition of dissolved organic matter in saline lakes of the Qing-Tibetan Plateau.
JO  - Org. Geochem.
VL  - 167
PY  - 2022
SN  - 0146-6380
ER  - 

TY  - JOUR
AB  - In this study, we conducted a detailed analysis of porewater downcore chemical properties and porewater dissolved organic matter (PDOM) composition using elemental C, N and S analysis, fluorescence spectroscopy, and ultrahigh resolution mass spectrometry (FT-ICR MS) at two contrasting sites in Chesapeake Bay. The sites, situated in the oligohaline upper bay and in the seasonally hypoxic mesohaline mid bay, receive fundamentally different detrital inputs predominantly from allochthonous and autochthonous sources, respectively. Unsurprisingly, we observed greater molecular oxygenation and degree of aromaticity in downcore PDOM profiles from the upper bay. At the mid bay station, PDOM composition was more indicative of non-aromatic algal-derived material. Unexpectedly, this autochthonous PDOM had lower C:S ratios. Hence, algal-derived organic matter appeared to be readily sulfurized, which was confirmed by quantification of dissolved organic sulfur as well as by qualitative interpretation of FT-ICR MS data. This finding suggests addition reactions of hydrogen sulfide to double bonds in unsaturated, but non-aromatic, organic molecules in autochthonous PDOM. Intriguingly, we also observed increases in humic-like fluorescence and dissolved organic carbon (DOC) concentrations in downcore PDOM profiles from both sites. Given the differences in molecular composition between sites, these results show that humic-like fluorescence can arise from different sources and biogeochemical processes. In the upper bay, we infer that these fluorescence signals reflect solubilization of terrestrially derived organic matter with a high aromatic and polyphenolic composition. By contrast, in the mid bay, these fluorescence peaks correlated negatively with hydrogen sulfide and are more likely linked to bacterial sulfate reduction.
AU  - Powers, L.C.*
AU  - Lapham, L.L.*
AU  - Malkin, S.Y.*
AU  - Heyes, A.*
AU  - Schmitt-Kopplin, P.
AU  - Gonsior, M.*
C1  - 63343
C2  - 51482
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England
TI  - Molecular and optical characterization reveals the preservation and sulfurization of chemically diverse porewater dissolved organic matter in oligohaline and brackish Chesapeake Bay sediments.
JO  - Org. Geochem.
VL  - 161
PB  - Pergamon-elsevier Science Ltd
PY  - 2021
SN  - 0146-6380
ER  - 

TY  - JOUR
AB  - We combined Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) and mass spectrometric analysis of stable carbon isotopes, a traditional method for tracking DOM sources, to investigate the variation in the complexity of water samples collected along a salinity gradient in Delaware Bay in March and August 2014. Detailed analyses of optical properties (ultraviolet and visible (UV-Vis) absorbance and excitation-emission matrix (EEM) fluorescence spectroscopy) were carried out. Results from statistical parallel factor analysis (PARAFAC) of EEM data were also used to track and further constrain fluorescent DOM (FDOM). Optical analyses and FT-ICR-MS data showed large differences between late winter and summer conditions, and the stable carbon isotopic composition was more variable in summer than in late winter. Although terrestrial inputs of DOM are evident at low salinities in both seasons, our data suggest that a significant source of FDOM, from either in situ water column production or from benthic aquatic or semi-aquatic plant communities, contributes DOM to low and mid-salinity waters in Delaware Bay during summer but not in late winter.
AU  - Powers, L.C.*
AU  - Luek, J.L.*
AU  - Schmitt-Kopplin, P.
AU  - Campbell, B.J.*
AU  - Magen, C.*
AU  - Cooper, L.W.*
AU  - Gonsior, M.*
C1  - 53838
C2  - 45064
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, England
SP  - 87-97
TI  - Seasonal changes in dissolved organic matter composition in Delaware Bay, USA in March and August 2014.
JO  - Org. Geochem.
VL  - 122
PB  - Pergamon-elsevier Science Ltd
PY  - 2018
SN  - 0146-6380
ER  - 

TY  - JOUR
AB  - This study investigates how changes in dissolved organic matter (DOM) quality can be evaluated considering all existing principal data pools from high field Fourier transform ion cyclotron mass spectrometry (FT-ICR-MS). We recommend five steps, including suggestions on underlying processes. Two different sediment profiles from a highly acidic mining lake in Germany with different mixis of the overlying lake water (dimictic vs. meromictic) were selected as a model for the analysis of sediment porewater sample to a depth of 30 cm. FT-ICR-MS datasets of elemental composition were evaluated for the presence of specific CHO molecular series. In six (seven) porewater depth groups of 63 (127) different data pools were identified. In the first step, the data pools were evaluated with components present in all six (seven) samples (total common presence). This group of components was analysed via a statistical rank analysis of the mass peak intensities (inter sample rankings analysis). The second step comprised the allocation of components which were not present in all samples to specific data pools (partial common presence and different presence pools). Of these pools the largest (containing most components) were selected in the third step for visualization of DOM quality change using van Krevelen diagrams. Underlying DOM transformations were discussed in the fourth step. The fifth step comprised the parallel allocation of changes in DOM quality and in concentrations of inorganic compounds. We identified the principal changes in both depth profiles and thereby demonstrated the potential of DOM data pool evaluation for elucidating biogeochemical processes.
AU  - Herzsprung, P.*
AU  - von Tümpling, W.*
AU  - Wendt-Potthoff, K.*
AU  - Hertkorn, N.
AU  - Harir, M.
AU  - Schmitt-Kopplin, P.
AU  - Friese, K.*
C1  - 51075
C2  - 42844
CY  - Oxford
SP  - 51-60
TI  - High field FT-ICR mass spectrometry data sets enlighten qualitative DOM alteration in lake sediment porewater profiles.
JO  - Org. Geochem.
VL  - 108
PB  - Pergamon-elsevier Science Ltd
PY  - 2017
SN  - 0146-6380
ER  - 

TY  - JOUR
AB  - Although the continuum of pyrolysed OM is an important part of soil OM (SOM) and therefore involved in global cycles, its formation and structural composition are not sufficiently known. Gaps in knowledge originate from methodological difficulties in detecting compounds formed via heating during vegetation burning. We therefore investigated soil samples (0-4 cm depth) from 33 yr treatments of periodic vegetation burning, mulching and natural succession at two grassland sites in Germany. Samples were investigated by way of X-ray absorption near edge structure (XANES) spectroscopy at the carbon (C) and nitrogen (N) K-edges, pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS), Py-single photon ionisation-MS (Py-SPI-MS) and Py-field ionisation MS (Py-FIMS). The XANES spectra differentiated the sites and indicated a relative enrichment in unsaturated C for the burned treatment at one site and substituted aromatic C and non-peptide N (nitriles and/or N in aromatic systems) at both sites. All three Py-MS methods distinguished the sampling sites via variation in content of polysaccharides, N-containing compounds and lignin derived substances. Vegetation burning depleted low molecular weight compounds (Py-SPI-MS and Py-FIMS) and formed high molecular substances (Py-SPI-MS and Py-FIMS) and some N-heterocyclic aromatic products (Py-GC-MS), which were only found in the burned samples. Furthermore, Py-FIMS revealed reaction products from m/z 614 to m/z 619 for both burned treatments. In general, all methods indicated the formation of N-heterocyclics and/or more recalcitrant SOM at almost equal total organic C and N content from periodic vegetation burning.
AU  - Kiersch, K.*
AU  - Kruse, J.*
AU  - Eckhardt, K.U.*
AU  - Fendt, A.
AU  - Streibel, T.
AU  - Zimmermann, R.
AU  - Broll, G.*
AU  - Leinweber, P.*
C1  - 7510
C2  - 29770
SP  - 8-20
TI  - Impact of grassland burning on soil organic matter as revealed by a synchrotron- and pyrolysis-mass spectrometry-based multi-methodological approach.
JO  - Org. Geochem.
VL  - 44
PB  - Pergamon-Elsevier
PY  - 2012
SN  - 0146-6380
ER  - 

TY  - JOUR
AB  - Rice fields are an important source for the greenhouse gas methane produced by acetoclastic and hydrogenotrophic methanogenesis. Fractionation of 13C/12C can in principle be used to quantify the relative contribution of these pathways, but our knowledge of isotopic fractionation during reduction of CO2 and turnover of acetate in different methanogenic environments is still scarce. We therefore measured ?13C signatures in two types of anoxic Italian rice field soils, one with high and one with low degradable organic matter (OM) content. Both soils were incubated in the presence and absence of methyl fluoride, a specific inhibitor of acetoclastic methanogenesis. Optimization of methyl fluoride concentration resulted in complete inhibition of acetoclastic methanogenesis. CH4 was then exclusively produced by hydrogenotrophic methanogenesis, allowing determination of the isotopic signatures and fractionation factors specific for this methanogenic pathway. Acetate, which was then no longer consumed, accumulated and was used for determination of the isotopic signature of the fermentatively produced acetate (both total acetate and methyl carbon of acetate). Hence, all isotopic signatures, including fractionation factors were determined for the methanogenic soil. These data, were then used for computation of the relative contribution of the two methanogenic pathways. In the high OM soil, the contribution of acetoclastic methanogenesis to total CH4 production increased simultaneously with decreasing acetate concentration. In the low OM soil, methanogenesis from H2/CO2 was clearly greater than theoretically expected. Furthermore, isotope fractionation of hydrogenotrophic methanogenesis indicated that the in situ energy status of methanogens strongly depended on the availability of organic carbon in the rice field soil system. Collectively, our data show that the study of isotopic fractionation in methanogenic environments allows a deeper insight into the ongoing processes, which may be quite different in the same ecosystem with different content of degradable OM.
AU  - Penning, H.
AU  - Conrad, R.*
C1  - 853
C2  - 24894
SP  - 2058-2069
TI  - Quantification of carbon flow from stable isotope fractionation in rice field soils with different organic matter content.
JO  - Org. Geochem.
VL  - 38
IS  - 12
PB  - Pergamon Press
PY  - 2007
SN  - 0146-6380
ER  - 

TY  - JOUR
AU  - Schäfer, T.*
AU  - Buckau, G.*
AU  - Artinger, R.*
AU  - Kim, J.I.*
AU  - Geyer, S.*
AU  - Wolf, M.
AU  - Bleam, W.F.*
AU  - Wirick, S.*
AU  - Jacobsen, C.*
C1  - 4716
C2  - 22539
SP  - 567-582
TI  - Origin and mobility of fulvic acids in the Gorleben aquifer system: implifications from isotopic data and carbon/sulfur XANES.
JO  - Org. Geochem.
VL  - 36
PY  - 2005
SN  - 0146-6380
ER  - 

TY  - JOUR
AB  - Aquatic humic substances from eight confined and unconfined aquifer/aquitard groundwater systems were analyzed for their stable carbon, radiocarbon, deuterium, and elemental contents. Fractionation of groundwater dissolved organic carbon (DOC) showed that humic substances are an important part of the organic solute load in all groundwaters. Groundwater humates are distinct from other terrestrial humates, and are characterized by low oxygen (36%) and high carbon (53%) contents. Elemental data from water table wells suggests this characteristic oxygen depletion is mainly a result of biochemical processes that occur in the vadose zone. The stable carbon isotopic composition of groundwater humates range between -31 and -24%. (PDB) with ann average of -26%., and reflect their terrestrial origins. The deuterium values of groundwater humate vary widely, and are mainly a reflection of 2H/H variability in the continental water cycle. Radiocarbon analyses suggest a predominant soil zone origin for most groundwater humates, although some groundwater systems are influenced to varying degrees by buried peat or coal. Soluble humate 14C mean residence times of up to several hundred years in the vadose zone before recharging to groundwater are due to the mixing of young and old organic carbon sources, rather than advective residence times.
AU  - Wassenaar, L.I.*
AU  - Aravena, R.A.*
AU  - Fritz, P.J.
AU  - Barker, J.F.*
C1  - 41139
C2  - 36388
SP  - 383-396
TI  - Isotopic composition (13C, 14C, 2H) and geochemistry of aquatic humic substances from groundwater.
JO  - Org. Geochem.
VL  - 15
IS  - 4
PY  - 1990
SN  - 0146-6380
ER  -